1. Field of the Invention
The present invention relates to search lights and more particularly to portable hand held search lights.
2. Description of the Prior Art
This invention is directed toward hand held search lights of the type which use high intensity lamps, such as xenon arc lamps or the like. Such lamps are frequently referred to as short arc lamps.
The search light contemplated by the invention has its principle use by sentries, police, rescue squads, and others for night time surveillance where high intensity light is required. In these uses, the search light frequently must be carried for long periods and used under adverse conditions. As such, the light should be light in weight, durable, and reliable. Further, it is contemplated that the light will be used in remote locations where trained service personnel are not readily available. To that end, the light must be easily serviceable by untrained personnel and the light must be designed to avoid dangers which can cause injury to such personnel when servicing and operating the light. Arc lamps have been known to explode during lamp replacement causing severe injury. Thus, a search light is desired which minimizes this danger. Further, complete subassembly change out should be easily accomplished without requiring special training in search light maintenance.
Further, it is desirable that such a search light be easy to operate without having to activate levers or cumbersome switches. The light used should also be easily operable by an operator to perform all lamp operations, such as beam focusing, high/low beam switching, etc. Such operations should be carried out at the touch of the operator's finger or thumb and should not require the use of two hands to operate the light. In addition, it is desirable that the light be remotely controllable so that it can be used in a stationary manner.
In order to provide reliability in such a search light, means must be provided to ensure that the proper voltages and currents are provided to insure that the arc lamp will always light under all conditions. For example, it requires a higher voltage to ignite a cold lamp than it does to ignite a hot lamp. It is well known that the electrodes of an arc lamp erode with usage. This further adds to the problem of insuring that the proper voltages and currents are always applied to the lamp to ensure reliable ignition and operation of the lamp.
The successful operation of a xenon lamp, or the like, requires a power supply capable of supplying a current regulated power source to insure proper operation of the lamp and to maximize its life. Three voltages are required to ignite an arc lamp and to bring it up to full and sustained operation: (i) a momentary high voltage RF pulse in the order of 10 to 50 kilovolts, applied across the two lamp electrodes (cathode and anode) and used to ionize the enclosed xenon gas; (ii) a momentary medium high voltage (called the open circuit voltage or plasma voltage) of the order of four to six times the nominal operating voltage of the lamp (e.g. 60 to 90 volts), applied across the lamp electrodes and which jumps the arc gap at the electrodes of the lamp at the moment that the high voltage gas ionizing pulse is applied across the lamp; and (iii) a low voltage, known as the sustainer voltage, of the order of 10 to 30 volts, applied across the lamp electrodes used to sustain the flow of the plasma after the open circuit voltage has been removed.
In prior art battery powered search lights, large high voltage transformers and storage capacitors have been required to generate a high voltage pulse of sufficient magnitude to fire the lamp spark gap. Further, these lights have required a separate voltage boosting circuit for generating the open circuit voltage, further adding to the size, weight, component count and complexity of the search light and its power supply circuitry.
It is well known that arc lamps place considerable current drain on the battery providing power to the lamp. As a result, frequent recharging of the battery is required. So far as it is known, prior art battery powered arc lamp type search lights always run at maximum light beam intensity, thus battery current drain is always at a maximum. A desirable feature in such a search light is to minimize this current drain and thus extend battery life. The present invention overcomes this disadvantage by providing to a normal or bright light mode of operation (with a low current drain) and a selectable alternate or brighter light mode of operation (with higher current drain).
As a battery life protection feature, it is desirable to detect low battery voltage and turn the light off before severe damage is done to the battery. However, if the light is so turned off, it is also desirable to provide an emergency override in case the user finds himself in a position requiring emergency light.
Ideally, a hand held search light should have a detachable battery for quick replacement and which can be detached from the light to reduce its weight. Thus, it can be seen that a need exists for a combination battery pack and hand held search light which enables the battery pack to be quickly released from the light and carried on a shoulder strap. This feature is advantageous when the light is to be carried for sustained periods. Such a feature further allows larger capacity battery packs to be carried when longer battery life is required. Further, it allows the battery pack to be quickly changed out without having to dismantle the light or remove any covers or caps from the light.
The safe mounting of xenon arc lamps in hand held search lights has always been of major concern to manufactures and users of such lights. Because these lights are subjected to dropping, and resultant shock, the lamp can explode if it is rigidly mounted in the light. Thus, a need exists for a means to shock mount an arc lamp which minimizes the possibility of such explosions. Resident with this shock mounting is the need to provide a means to remotely focus the light beam and to center the beam in the focal plane of the light without disrupting the shock mounting.
Further, it is desirable that any combination shock mounting, focusing, and centering mechanism be designed such that an inexperienced person can replace the lamp without fear of explosion and adjust the lamp without fear of injury by exposure to high intensity light (ultra violet) from the lamp after its replacement.
I have found that prior art arc lamp type search lights are not designed to maximize the amount of light collected and emitted by the lamps reflector or mirror. Thus, in order to achieve a satisfactorily bright light, it has been necessary to use a large lamp with attendant large power supply and battery. I have discovered an improved combination of mirror and arc lamp design which at least doubles the mirror light collection efficiency, thus enabling my search light to generate much more light with less power consumption than prior art lights using comparable voltage arc lamps.
Various types of spotlights and search lights, some of which use arc lamps and which disclose lamp focusing and mounting mechanisms and circuits for operating such lights, are disclosed in U.S. Pat. Nos. 3,746,920; 3,675,078; 1,286,590; 1,291,483; 3,201,580; 4,240,009; 1,369,892; 3,689,759; 4,499,525; 1,825,354; 4,634,936; 2,982,881; 4,121,136; 4,782,432; 4,787,022; 4,317,162; 4,533,984; and 4,450,508.